Using water to spray across the flow path of a gas, particularly air, as it traverses a housing or chamber for the purpose of filtering, washing and cooling the gas takes many forms. In some cases nozzles are mounted around the periphery of the chamber to spray water toward its center. In other cases, a foraminous wall receives water sprayed or trickled from above such that it flows downward by gravity as the gas passes therethrough. Additionally, numerous patents disclose a rotating drum, cylinder or disc mounted either parallel or perpendicular to the flow of gas. The rotating drum, etc. flings water in a pattern across the flow path of gas passing through the chamber and the water tends to clean and cool the air.
There are three basic types of rotary spraying apparatus known in the art, namely smooth cylinders, smooth discs, and patterned or toothed discs; the latter comprise discs bearing projections extending out of the plane of the discs.
Smooth cylinders are bulky and so heavy that they are difficult to balance on a shaft revolving at high speed. In addition, since the water or other liquid being sprayed only adheres to the surface of the cylinder by surface tension, the quantity of water sprayed by a smooth cylinder is small relative to the large power needed to rotate a heavy cylinder at high speed.
Smooth discs are lighter and easier to balance than smooth cylinders but spray only a small amount of water. Accordingly, a very large number of discs may be necessary where large quantities of water have to be sprayed.
Toothed discs spray far more water than smooth discs because the projections act as scoops lifting water out of the bath. Unfortunately, the spray produced by known apparatus using toothed discs lacks uniformity, both as regards to the sizes of individual droplets within the spray and the angular dispersion of the spray.